Medicament delivery devices such as auto-injectors and inhalers nowadays provide possibilities for the users themselves to handle medicament delivery in an easy, safe and reliable manner. Moreover, such devices also facilitate the administration of drugs for hospital personnel.
A number of functions for medicament delivery devices have been developed such as controlled injection rate and multiple doses with means for varying the quantity of each dose.
EP1843808 B1 discloses a device for delivering a medicament which has the capability to adjust the dose. In particular, EP1843808 B1 discloses an injection device comprising a longitudinally movable piston and a spring arrangement acting on the piston and capable of exerting a force on the components, a first holding means arranged and capable of holding the piston in a force-loaded state, and an activator means capable of acting on the first holding means for releasing the piston. The dose can be set by turning a dose setting knob, so that a dose quantity indication for the chosen dose, on the outside of the main upper housing, is in register with an indication mark on the knob. The turning of the knob causes the dose setting sleeve also to turn. The turning of the knob and the dose setting sleeve causes a rear nut to turn because the rear nut has ledges positioned in a groove of the sleeve. Turning of the knob and thus the dose setting sleeve furthermore causes the rear nut to move along the piston due to its threads being in engagement with the threads of the piston. This creates a distance between the rear nut and a front nut and sets the axial distance that the piston can move during medicament delivery. The dose can thereby be set.